Water-based paints and coatings are used on a large scale industrially. Critical to effective wetting of the substrate is the lowering of the surface tension of the aqueous system by means of a surfactant. It is not only the lowering of the static surface tension to a small value that is decisive here, but also the corresponding lowering of the dynamic surface tension. A low dynamic surface tension is needed in particular for high-speed applications: for example, when applying coatings by spraying, or in printing operations. Furthermore, the surfactants used must not create any surface defects, must not cause any turbidity, and should be low-foaming. That means, they should not promote the build-up of significant amounts of foam.
Although nonionic surfactants such as alkylaryl ethoxylates or alcohol ethoxylates or ethylene oxide (EO)-propylene oxide (PO) copolymers are for sure capable of reducing the static surface tension, the high molecular weight and resultant low molecular mobility of these classes of compounds mean that it is not possible to lower the dynamic surface tension to a value which is acceptable to the user.
Conversely, some anionic surfactants, such as the sodium salts of monoalkyl or dialkyl sulfosuccinates, are able effectively to reduce the dynamic surface tension, but using them leads to severe build-up of foam in application, and the finished coating reacts sensitively to water.
More recently a new class of surfactants has been developed based on acetylenic glycols and their alkoxylates. The properties of these surfactants are situated between those of the surfactants outlined above. With these new surfactants it is possible to reduce both the static and the dynamic surface tension, with the values which can be achieved not entirely matching those of the nonionic and anionic surfactants. But, on the plus side, these surfactants provide comparatively low-foam formulations (EP-B-0 897 744, U.S. Pat. No. 2,997,447).
In view of these properties, surfactants of this kind have been able to establish themselves convincingly in numerous applications. Their properties are primarily attributed to the rigid acetylenic alkyl spacer, which, as a result of the restricted degrees of freedom, dictates a kind of preorientation of polar and nonpolar groups. Responsibility for these properties is additionally ascribed to the small distance between the polar groups and to the low molecular weight (<300 g/mol), which allows the surfactant molecules to be highly mobile.
A problem with compounds of this type is that, in applications, foam build-up reoccurs after a very short time. For the user, on the other hand, it is very important to prevent this new foam build-up for as long as possible. The alternative would be to add defoamers, whose possible consequences include unwanted defects of the coating film and problems with interlayer adhesion.
There was therefore a need to provide compounds which not only allow effective reduction in static and dynamic surface tension but also prevent foam build-up/new foam build-up effectively for a long period of time; i.e., e.g., a time period greater than 60 seconds.
In an effort to overcome the disadvantages of the prior art and to provide compounds which significantly reduce dynamic surface tension and at the same time effectively inhibit the (re)formation of foam for a long time it has now surprisingly been found that this objective can be achieved by means of amino alcohols preparable by reacting amines, preferably secondary amines, containing at least one amine hydrogen with glycidyl compounds.